Numbering presses for carrying out numbering of printed documents are already known in the art. Such a numbering press is for instance disclosed in German patent application No. DE 1 486 894 or European patent application No. EP 0 061 795. FIG. 1 is a drawing taken from European patent application No. EP 0 061 795 which schematically illustrates a numbering press.
As illustrated in FIG. 1, such numbering press typically comprises a printing unit 1 equipped with an impression cylinder 2 and a numbering unit 3 cooperating with the impression cylinder 2. A continuous web or individual sheets to be printed is/are fed to the impression cylinder 2 using known transfer means (not illustrated in FIG. 1). Once printed, the web or sheets is/are fed to a delivery unit (not illustrated in FIG. 1).
The numbering unit 3 typically comprises at least one numbering cylinder 4 which is inked by a known inking system 5. In the field of numbering of banknotes, it is common to have at least two such numbering units 3 cooperating with the same impression cylinder 2 so as to print two serial numbers on each banknote.
In the field of printing of banknotes, a plurality of banknote prints are printed on successive sheets or web portions in the form of arrays having a determined number of columns and rows. These sheets or web portions are ultimately cut into individual banknotes at the end of the printing process. When carrying out numbering of such sheets or web portions, the numbering press has to be equipped with a numbering cylinder comprising as many numbering devices as there are positions to be numbered on each sheet or web portion.
FIG. 2 is a partial cross-section view of a typical numbering cylinder 4 used for numbering several positions on a sheet or web portion, which partial cross-section view is taken along the axis of rotation of the numbering cylinder 4. The numbering cylinder 4 commonly comprises a shaft 41 bearing a plurality of supporting discs 42 (only one being shown in FIG. 2). Each supporting disc 42 carries a plurality of numbering devices (or numbering boxes) 6 which are distributed around the periphery of the supporting disc 42 (only one numbering device 6 being shown in FIG. 2). Each numbering device 6 typically comprises a housing 60 with a plurality of rotatable numbering wheels 61 disposed one next to the other around a common shaft. It will be appreciated that the numbering cylinder 4 comprises as many supporting discs 42 as there are columns of prints to be numbered on the sheets or web portions and that each supporting disc 42 comprises as many numbering devices 6 as there are rows of prints to be numbered on the sheets or web portions.
When using mechanically-actuated numbering devices, mechanical actuation means are additionally provided in order to adequately actuate the numbering wheels 61 of each numbering device 6. To this end, mechanically-actuated numbering devices 6 usually comprise a switch lever 66 for actuating the numbering wheels 61, which switch lever 66 cooperates with a switch cam disc 71 via a switch cam follower 67 (there being as many switch cam discs 71 as there are supporting discs 42). Each switch cam disc 71 is fixed with respect to the rotation of the numbering cylinder 4 and carries a cam surface (not shown) designed to initiate actuation of the numbering devices 6 between each numbering iteration. More detailed explanation about such actuation means might be found for instance in U.S. Pat. No. 3,377,948 or European patent application EP 0 718 112.
In instances where mechanically-autonomous electronic numbering devices are used, such mechanical actuation means might not at all be necessary. This is for instance the case of the numbering device disclosed in European patent application No. 06115994.3 filed on Jun. 23, 2006 in the name of the present Applicant and entitled “NUMBERING DEVICE FOR TYPOGRAPHIC NUMBERING”.
Further numbering devices are also disclosed in U.S. Pat. No. 4,677,910, International application No. WO 2004/016433, German patent application No. DE 30 47 390, U.S. Pat. No. 4,843,959, International application No. WO 2005/018945, as well as European patent application No. 05405375.6 filed on Jun. 8, 2005, which is now European Patent No. 1 731 324 A1, in the name of the present Applicant and entitled “NUMBERING PROCESS FOR SECURITIES, METHOD FOR PROCESSING THE NUMBERED SECURITIES AND NUMBERING DEVICE TO CARRY OUT THE NUMBERING PROCESS”.
As shown in FIG. 2, each numbering device 6 is mounted on a peripheral mounting ring 43 provided on the periphery of the supporting disc 42. This peripheral mounting ring 43 typically exhibits a dovetailed cross-section, as shown in FIG. 2. Each numbering device 6 comprises a corresponding dovetailed mounting groove 63 conforming to the shape of the peripheral mounting ring 43, as well as a clamping mechanism 65 for clamping the numbering device 6 in position onto the peripheral mounting ring 43. This clamping mechanism 65 typically includes a clamping part that is moveable with respect to the housing of the numbering device 6 and that can be displaced laterally (usually by means of screws, not illustrated in FIG. 2) towards one side of the peripheral mounting ring 43 so as to shorten the gap of the mounting groove 63 and thereby secure the numbering device 6 onto the peripheral mounting ring 43.
A problem with the dovetail mounting discussed above resides in the fact that there remains a substantial risk that the numbering devices loosen from the peripheral mounting ring 43 and get detached from the supporting discs 42, thereby causing considerable damage not only to the numbering devices themselves but also to the printing press in which they are mounted.
Adjustment of the position of the numbering devices about the peripheral mounting ring is furthermore rather difficult as it implies unscrewing and screwing of the clamping part of the clamping mechanism.
In addition, the dovetail mounting requires that the mounting ring 43 and mounting groove 63 match together, i.e. exhibit a similar curvature following that of the supporting discs 42 on which the numbering devices 6 are mounted. This means that each numbering device has to be designed in correspondence with the diameter of the numbering cylinder on which they are meant to be mounted and that a numbering device designed for a given numbering cylinder diameter will not fit on a numbering cylinder having a different diameter.
There is therefore a need for an improved solution for mounting numbering devices onto numbering cylinders of printing presses.